Cartilage acts as a pad between bones to reduce friction and prevent the bones from grinding against one another. Cartilage covers the articular surface of many, if not all, joints in the body. The smoothness and thickness of the cartilage are factors that determine the load-bearing characteristics and mobility of the joints. Over time, due to injury or heredity, however, lesions such as fissures, cracks or crazes can form in the cartilage. In some cases, osteochondral, the lesion penetrates to the subchondral surface of the bone. In other cases, chondral, the lesion does not penetrate to the subchondral surface of the bone. In any event, lesions generally do not repair themselves—and if any repair is made it is insufficient to heal—leading to significant pain and disability, either acutely or over time. Thus, there has long been a need to treat, repair, or regenerate damaged articular cartilage.
One approach for regenerating new cartilage is autologous chondrocyte transplantation. However, this technique is complex and relatively costly. Other techniques, aimed at repair instead of regeneration, include debridement, lavage, microfracturing, drilling, and abrasion arthroplasty. These procedures generally involve penetrating the region of vascularization in the subchondral bone with an instrument until bleeding occurs. Formation of a fibrin clot differentiates into fibrocartilage, which then covers the defect site. Some have found, however, that the resulting repair tissue is relatively weak, disorganized, and lacks the biomechanical properties of normal hyaline cartilage that typically covers the bone ends. Additionally, this technique can generally only be used on chondral defects in the presence of normal joint congruity.
An alternative approach has been to undergo a total replacement of the joint. Such total replacements, however, are costly, high risk, and involve a long recovery time. Accordingly, there is a need for alternative treatments.
The above-identified prior art devices and methods, as well as alternative devices and methods, are illustrated in greater detail in the following patents and patent publications:
U.S. Patent Pub. No. 2005/0137708 to Clark discloses, inter alia, a knee joint resurfacing implant that may include femoral implant and tibial implant components. The femoral implant components may be attached to the femur using screws or other fixation devices, and may be configured to share loads between cortical and cancellous bone material. The tibial implant components are formed in modular portions which may be assembled within the knee joint and may be free-floating or fixed to the tibial surface.
U.S. Patent Pub. No. 2007/0032876 to Clark discloses, inter alia, a knee joint prosthesis including femoral and tibial components. The bodies of the components may possess a network of channels which may be used to deliver bone cement to the component bone interface after the components are implanted.
U.S. Patent Pub. No. 2007/0250169 to Lang discloses, inter alia, methods and devices for repairing articular surfaces. The devices of Lang are customizable, or patient specific, implants configured for placement between joint surfaces formed by inserting a hollow device having an aperture and a lumen into a target joint, and injecting material into the hollow device to form an implant.
U.S. Pat. No. 6,679,917 to Ek discloses, inter alia, an implant for installation into a portion of an articular surface including a protrusion configured to cover an un-excised portion of articular surface proximate to the implant.
U.S. Pat. No. 6,814,757 to Kopylov, et al. discloses, inter alia, a joint surface replacement or joint prosthesis for the distal radioulnar joint.
Accordingly, what is needed is a minimally invasive, cost effective, implant, which preserves as much of the normal, natural, cartilage as possible. Also needed is an implant that restores much of the patient's range of motion, maintains that restored motion over a long period of time, and requires a relatively short rehabilitation period.